Memory metals in general change shape and have unusually large expansion coefficients in a specific temperature range known as the metal's transition temperature range. These phenomena are most commonly described by those of skill in the art as superelasticity and shape memory. By applying heat to a memory metal in its transition temperature range, such metal can be made to expand to a greater extent in a shorter period of time than ordinary metals.
NITINOL (Nickel Titanium Naval Ordnance Laboratory), which contains nearly equal portions of nickel and titanium, is one of the more common memory metals. Its shape memory properties have been used in the manufacture of pipe couplings, connectors and actuators. Most recently, memory metals in general have been finding applications as actuators and artificial muscles in robotic applications.